Heterocyclic antistain agents



United States PatentfO HETEROCYCLIC ANTISTAIN AGENTS Charles F. H. Allen and Paul W. Vittum, Rochester, N. Y. assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey No Drawing. Application December 24, 1952, Serial No. 327,941

5 Claims. (Cl. 95-6) This invention relates to color photography and particularly to a method for preventing the formation of color fog or stain in photographic emulsions.

The method of color photography in which color-forming or coupler compounds combine with the development product of aromatic amino photographic developers to produce dyes is well known. The color formers or couplers may be added directly to the emulsion layers or may be incorporated in the developing solution as described in Fischer U. S. Patent 1,102,028, granted June 30, 1914, or they may be incorporated in a water-permeable medium which is insoluble in the carrier for the sensitive silver salt as described in Mannes and Godowsky U. S. Patent 2,304,940, December 15, 1942, and Jelley and Vittum U. S. Patent 2,322,027, granted June 15, 1943.

A difficulty frequently encountered in these processes is the formation of color fog or stain. When the exposed material is developed in a color-forming developer, dye fog is frequently formed in the emulsion layer. This is because the developing agent has been oxidized to some extent by the action of the air and the oxidized developer tends to couple with the color-forming compound at places in the photographic material where no silver image is produced. It is well known that in these processes the dye should be formed only where the silver halide is reduced to metallic silver, thereby oxidizing the developing agent to a form which couples with the color former. Once the developing agent is oxidized, it couples immediately with the color former whether a photographic image is present or not. Aerial oxidation of the developer or oxidation by means other than the photographic image therefore converts the developer to a form which will immediately react with the color former to produce a color fog or stain. This effect is especially noticeable in materials having couplers incorporated in the sensitive layer since there is no coupler in the developing solution to react with any developing agent which is oxidized by the action of the air. Fog or stain arising from these causes is not readily controlled by the same procedures used to control silver fog.

The control of color fog or stain by incorporating various compounds in photographic emulsions has been described in Weissberger and Vittum U. S. Patent 2,356,486,

August 22, 194-4, and Vittum and Wilder U. S. Patent 2,360,290, October 10, 1944. However, the use of these simple reducing agents for preventing or controlling color fog or stain has a distinct disadvantage in that they have a tendency to wander from the areas in which they have been placed into other areas of the photographic composition where they have harmful effects. In certain color processes the compounds are placed in the area of the emulsion containing the coupler and act on it to produce undesired effects as will be explained more fully hereinafter.

Antistain agents for direct incorporation in photographic emulsion layers must fulfill certain requirements such as the following:

1. They must be easily compatible with and substantially non-diffusing in the colloid of the photographic layer.

2. They must have a strong enough reducing action so that they react rapidly with the oxidized color developer. Their action as antistain agents presumably depends upon their ability to reduce the oxidized developer formed in the highlight areas of the image.

3. They must be of such a nature that they do not give rise to highly colored oxidation products, so that when the material containing them is put through an oxidizing bath such as a silver bleach bath they do not themselves give rise to stain.

It is, therefore, an object of the present invention to provide antistain agents which are easily compatible with and non-diffusing in the colloid of the photographic layer in which they are incorporated. A further object is to provide antistain agents which are non-diffusing in the photographic layer and which are strong enough reducing agents to react rapidly with oxidized color developer. A further object is to provide antistain agents which do not form highly colored oxidation products when the material containing them is put through an oxidizing bath. Other objects will appear from the following description of our invention.

' These objects are accomplished by the use in an emulsion or other layer of a photographic material of a compound having the structure Antistain agents useful according to our invention are:

3,4-dihydroxy-2,fi-dicarbomethoxyfuran O-OH ' CHaOzC g 3,4'dihydroxy-2,5-dicarbomethoxythiophene 3. HOC COH 3,4-dihydroxy-2,E-diphenylthiophenedioxide The antistain agents of our invention are useful in emulsion layers containing water-soluble non-diffusing;

color couplers of the type described in Fischer U. S. Patent 1,102,028. Our agents may also be used in emulsions,

of the type described in Mannes and Godowsky U. S. Patent 2,304,940 and Jelley and-Vittum U. S. Patent 2,322;- 027 where the coupler is present in a dispersed hydrophobic solvent.

The antistain agents of our invention may also be used in non-sensitive overcoating or filter layers such as a colloidal silver interlayer of multilayer photographic material. The incorporation of our antistain agents in a photographic emulsion is illustrated by the following example:

One gram of the magenta coupler, 1-[p-(p-tert. butyl phenoxy)phenyl] 3 [u (p-tert. butylphenoxy)propionylamino]--pyrazolone (Porter and Weissberger U. S. Patent 2,369,489Compound 47) was dissolved at 130 C. in 3 cc. of di-n-butylphthalate. To this hot solution there was added 0.2 gram of 3,4-dihydroxy-2,5-dicarbomethoxy thiophene and the resulting solution was poured with stirring into a solution containing 18 cc. of gelatin solution, 2 cc. of water and 2 cc. of 1.0% Alkanol B (sodium triiso propyl naphthalene sulfonate). The whole mixture was then passed several times through a colloid mill. The resulting fine dispersion was then added, at 40 C., to 50 cc. of a melted positive type silver halide emulsion and the whole was well mixed and coated on a suitable support. Upon color development with a primary aromatic amino developing agent, this coating gave a bright magenta dye image and showed a marked reduction in stain over a similar material prepared without the antistain agent.

In general, the antistain agents of our invention are used in the emulsion or other layer in quantities ranging from 0.07 gram to 4.3 grams per liter of emulsion or gelatin solution. These values are, however, merely illustrative.

In certain cases, the antistain agents of our invention may be incorporated in a processing solution such as a pre-bath, first developer bath, or color-forming developer used with colored film which is developed with a primary aromatic amino developing agent.

Our agents are particularly useful with color-forming emulsions coated on paper supports Where it is especially important to reduce the minimum or fog densities. This applies both to negative developed paper and to reversal paper as well as to transparency materials.

The compounds of our invention are prepared as follows:

Compounds 1 to 3 were prepared as described in J. A. C. 8., vol. 71 (1949), page 4089. Compound 4 was prepared as described in J. A. C. 8., vol. 72 (1950), page 2856.

It will be understood that the examples and modifications described herein are illustrative only and that our invention is to be taken as limited only by the scope of the appended claims.

We claim:

1. A color-forming photographic emulsion having reduced fogging tendency, comprising a silver halide emulsion having incorporated therein a non-diffusing coupler compound capable of coupling with the oxidation product of a primary aromatic amino color developer and a nondiffusing antistain agent having the structure in which R is a hydrocarbon radical, n is a positive integer from 1 to 2 and Z is selected from the class consisting of oxygen, sulfur and nitrogen atoms.

2. A color-forming photographic emulsion having reduced fogging tendency, comprising a silver halide emulsion having incorporated therein a non-diltusing coupler compound capable of coupling with the oxidation product of a primary aromatic amino color developer and 3,4- dihydroxy-2,5-dicarbomethoxy furan as an antistain agent.

3. A color-forming photographic emulsion having reduced fogging tendency, comprising a silver halide emulsion having incorporated therein a non-diffusing coupler compound capable of coupling with the oxidation product of a primary aromatic amino color developer and 3,4-dihydroxy-Z,S-dicarbomethoxy thiophene as an antistain agent.

4. A color-forming photographic emulsion having reduced fogging tendency, comprising a silver halide emulsion having incorporated therein a non-diffusing coupler compound capable of coupling with the oxidation prodnot of a primary aromatic amino color developer and 3,4- dihydroxy-2,5-dicarboethoxy-N-ethyl pyrrole.

5. A color-forming photographic emulsion having reduced fogging tendency, comprising a silver halide emulsion having incorporated therein a non-ditfusing coupler compound capable of coupling with the oxidation product of a primary aromatic amino color developer and 3,4-dihydroxy-2,5-diphenyl thiophene dioxide as an antistain agent.

References Cited in the file of this patent FOREIGN PATENTS 557,802 Great Britain Dec. 6, 1943 OTHER REFERENCES I. A. C. S., vol. 71, (1949), page 4089.

I. A C. 8., vol. 72 (1950), page 2856. 

1. A COLOR-FORMING PHOTOGRAPHIC EMULSION HAVING REDUCED FOGGING TENDENCY, COMPRISING A SILVER HALIDE EMULSION HAVING INCORPORATED THEREIN A NON-DIFFUSING COUPLER COMPOUND CAPABLE OF COUPLING WITH THE OXIDATION PRODUCT OF A PRIMARY AROMATIC AMINO COLOR DEVELOPER AND A NONDIFFUSING ANTISTAIN AGENT HAVING THE STRUCTURE 